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Saturday, December 10, 2011

[Yasmin_discussions] Fwd: [Yasmin_an] Synaesthesia in Chimpanzees

yasminers

fascinating post by sean day which states:

Thus, we are called upon, here, to re-asses our definitions of "thesenses" and "modes", and, thus, also, "cross-modal".

here is the abstract of the article Sean Day pointed us to

roger

Humans share implicit preferences for certain cross-sensorycombinations; for example, they consistently associate higher-pitchedsounds with lighter colors, smaller size, and spikier shapes. In thecondition of synesthesia, people may experience such cross-modalcorrespondences to a perceptual degree (e.g., literally seeingsounds). So far, no study has addressed the question whether nonhumananimals share cross-modal correspondences as well. To establish theevolutionary origins of cross-modal mappings, we tested whetherchimpanzees (Pan troglodytes) also associate higher pitch with higherluminance. Thirty-three humans and six chimpanzees were required toclassify black and white squares according to their color whilehearing irrelevant background sounds that were either high-pitched orlow-pitched. Both species performed better when the background soundwas congruent (high-pitched for white, low-pitched for black) thanwhen it was incongruent (low-pitched for white, high-pitched forblack). An inherent tendency to pair high pitch with high luminancehence evolved before the human lineage split from that of chimpanzees.Rather than being a culturally learned or a linguistic phenomenon,this mapping constitutes a basic feature of the primate sensorysystem.

The last common ancestor of chimpanzees and humans (CHLCA) existedsomewhere between 7 and 10 million years ago (mya). So, we can pushcross-modal correspondences in our ancestry back to at least 7 mya,and note that not only was it persistent in the genera leading up tomodern-day species of Pan, but, apparently, would also have appearedin (at least) genera Sahelanthropus, Ardipithecus, andAustraolopithecus, on the way to genus Homo. Which implies also thatcross-modal correspondences would have occurred amongst Homo sapiens'previous companion species erectus, Denisovans, Neanderthals, andflorensiensis.

I will posit the following: "Synesthesia", by force of its basicdefinition, must be the minority circumstance for a given species."Synesthesia" means an (atypical) combining of what are,statistically, most commonly un-combined sensory perceptions.

Now, if, as Ludwig et al. 2011 suggests, cross-modal correspondencescan be traced back in our line to at least 7 mya with the CHLCA, and,as Marks, Cytowic, Ramachandran, and many other synesthesiaresearchers have pointed out, is so pervasive in modern-day humans -then that is not "synesthesia". It is also not "cross-modalcorrespondence".

Rather, that is how the human senses most typically - statistically - work.

Thus, we are called upon, here, to re-asses our definitions of "thesenses" and "modes", and, thus, also, "cross-modal".

Again, for something to be "cross-modal", that implies that there are,indeed, two separate modes, and that a correspondence between themwould, given the odds, be more unlikely. If, however, suchcorrespondences are the more common event - as, apparently, they arefor humans regarding, e.g., luminance and (sound) pitch (frequency) -then that is how our perception most commonly works, and we need tore-evaluate what we now increasingly see are outdated paradigmsregarding "the senses" and "perceptual modes".

Much of what is currently being labeled "cross-modal correspondence"is not. For something to be a cross-modal correspondence, that, too,would have to be the less likely event.

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